This invention generally relates to electronic systems and in particular it relates to voltage regulators.
Many electronic circuits use amplifiers to manipulate various signals within the circuit. The output of the amplifier may be connected to provide an output voltage to a load circuit. The design of the output stage may affect various operating aspects of the amplifier. For example, some amplifiers can deliver a high output current to the load. Other amplifiers can produce an output voltage swing that is approximately equal to the magnitude of the power supply for the amplifier circuit. Some amplifiers must provide an output that has a low crossover distortion. Yet other amplifiers are required to maintain gain and stability at relatively high frequencies. Each of these requirements places constraints upon the design of the output stage.
During operation, an amplifier circuit consumes current from a power supply. A portion of this current, known as the quiescent current, is used to bias the internal circuitry of the amplifier. Trends in IC design (especially battery-powered applications) are requiring supply currents (quiescent currents) to decrease. In amplifiers, the large signal transient response or slew rate is directly related to the quiescent current in the output stage.
Generally, and in one form of the invention, the low dropout voltage regulator circuit includes: a MOS pass through transistor;
a resistor feedback circuit coupled to the MOS pass through transistor; an amplifier having an input coupled to the resistor feedback circuit; a Class A output stage coupled between an output of the amplifier and a gate of the MOS pass through transistor; and
a speedup circuit coupled between the output of the amplifier and the gate of the MOS pass through transistor.